The Convention establishes standards and regulations for discharge of ballast water and sediments from ships so as to control the discharge of harmful aquatic organisms and pathogens causing injury to the environment, human health, property and resources. The Convention specifically takes note of the objectives of the 1992 Convention on Biological Diversity as to the conservation and sustainable use of biological diversity and marine coastal ecosystems, and to the threat posed by alien species to these ecosystems, as well as to habitats and species.
The Convention standards for ballast water treatment including Regulation D-2 Ballast Water Performance Standard are:                1 Ships conducting Ballast Water Management in accordance with this regulation shall discharge less than 10 viable organisms per cubic metre greater than or equal to 50 micrometres in minimum dimension and less than 10 viable organisms per milliliter less than 50 micrometres in minimum dimension and greater than or equal to 10 micrometres in minimum dimension; and discharge of the indicator microbes shall not exceed the specified concentrations described in para2graph 2.        2 Indicator microbes, as a human health standard, shall include:        .1 Toxicogenic Vibrio cholerae (O1 and O139) with less than 1 colony forming unit (cfu) per 100 milliliters or less than 1 cfu per 1 gram (wet weight) zooplankton samples;        .2 Escherichia coli less than 250 cfu per 100 milliliters;        .3 Intestinal Enterococci less than 100 cfu per 100 milliliters.        
Viable organisms of Reg. D-2(1) greater than or equal to 50 micrometres in minimum dimension are removed from ballast water to a level of less than 10 viable organisms per cubic meter by means of commercially available filtration devices equipped with 40 micron filtering screens.
Ballast water discharged from a commercially available 40 micron filter device requires further treatment for (i) the removal of organisms less than 50 micrometres in minimum dimension and greater than or equal to 10 micrometres in minimum dimension to a level of less than 10 viable organisms per millilitre, and (ii) removal of indicator microbes to the levels recited in Reg. D-2(2) above.
In the art of purifying water, ultraviolet light is well known as having a biocidal and bactericidal effect on organisms and microbes and is often used with ozone, photo-catalysts, and other substances to achieve a desired effect on organisms.
U.S. Pat. No. 5,322,569 to Titus prevents biofouling of underwater objects by ultraviolet irradiation. Marine biofouling is avoided by irradiation of specific surfaces of under water objects with ultraviolet light to prevent attachment of organisms to those surfaces, to stun the organisms prior to removal, or to exterminate organisms at specific surfaces or over a defined volume. Titus employs ultraviolet light having a wavelength of 250.+−.10 nanometers and providing a minimum irradiation intensity of 20.mu.watt/cm.sup.2 at a distance of at least two feet. Conventional ultraviolet light sources such as mercury, mercury/xenon, and xenon lamps have been found to provide satisfactory ultraviolet power output.
U.S. Pat. No. 6,358,478 to Söremark is directed to the treatment of fluids and generates ozone for its oxidizing effect. UV radiation at a frequency of 180 nm is known to generate ozone which by exposure to the radiation is broken down to obtain free radicals. A combination of ozone, oxygen, hydroperoxide and UV radiation provides quick and efficient generation of free radicals. Microorganisms are inactivated with the aid of ozone and radicals as an oxidation reaction. The membrane of the organism is first attacked by radicals, and thereafter radicals destroy nuclear material inside the cell/virus/spore.
U.S. Pat. No. 6,092,653 to Carmignani is directed to purification and disinfection of fluids using semiconductor photocatalysts notably titanium dioxide and ultraviolet radiation in a device where fluid to be purified has intimate contact with semiconductor surfaces while spreading activating UV light over as large a surface area as is practical.
U.S. Pat. No. 7,081,636 to Morazzi discloses that it is known to use ultraviolet (UV) radiation in sterilisation systems for use in the purification of water and the sanitisation of a variety of items. The UV radiation and any ozone produced by the UV radiation with oxygen in the air acts to kill bacteria and germs. It is also known to use ultraviolet (UV) radiation for a variety of other uses including those involving the promotion of photochemical reactions and of molecular dissociation. One problem such systems is that it is difficult to efficiently provide sufficient excitation energy to the UV source and difficult to effectively transfer that energy to the substance or entity to be treated. It is therefore difficult to arrange systems for high energy, high throughput industrial purposes. Accordingly, Morazzi provides an ultraviolet light source comprising an ultraviolet bulb; a pulsed microwave energy source for exciting said ultraviolet bulb; and an optically transparent waveguide for guiding pulsed microwave energy originating from said pulsed microwave energy source to the ultraviolet bulb. The waveguide wholly surrounds the ultraviolet bulb. In one aspect, the dominant wavelength of the ultraviolet light source is from 240 nm to 310 nm, particularly 254 nm. Such wavelengths have been found to be particularly useful for sterilisation, purification or sanitisation applications.
So, while UV irradiation is known for killing organisms, it is nonetheless necessary to utilize UV radiation in a specific system in order to achieve desired purification effects in fluids.
Applicants in this invention provide a method and apparatus using ultraviolet radiation with specific reference to reducing organisms and microbes in treatment of ships ballast water.